If you’ve been wondering exactly why Microsoft has taken so long to unwrap Windows Phone 8.1 to the world, today’s leaks explain everything. As the company has begun sharing the Windows Phone 8.1 SDK to developers yesterday, it was only a matter of time before we had all the goods on what to expect for the update, and the list is insanely big. To avoid any confusion, let’s just go through the major changes.

Apps merge

Microsoft has been hinting about “Universal Apps” for quite some time. The SDK does show this feature to be included, though this is just similar to what we currently see in iOS and Android, but not exactly the same. The apps do have shared HTML and JavaScript code, but it will be up to the developer to merge these and make them available on both the Windows Phone Store and the Windows Store.

Microsoft is also changing the distribution file format for apps, and following the same Windows 8 scheme of .appx, though there is no hint of these apps also working on Windows 8.1, so do keep this in mind. We do see a significant push into making Windows RT and Windows Phone the same operating system, but the merger between them won’t be final for Windows Phone 8.1, or at least not in the current SDK being leaked.

Lots and lots of feature changes

The list of changes is so significant, that we wonder if the developer leaking this was able to see it all. The biggest change is that Windows Phone is becoming more customizable. Just like you can currently select different camera lenses and camera apps, you’ll also be able to select a different app for text messaging, as you can with Android. We also see the inclusion of VPN support, a major request for years now. There is also a new “Battery Power Sense” feature to finally monitor and track battery life, and we also see the rebranding of SkyDrive to OneDrive, aside from the Music+Video app to be now separated into separate services. You’ll also notice that the camera app is changed as well, and resembles more of what we currently see from Nokia Lumia smartphones, aside from the fact that we’ll now have a burst-mode included.

A couple of additional major changes include the fact that the operating system also includes a new Storage Sense feature that allows you to send apps to your microSD card if necessary. We also see changes in the way the operating system multi-tasks, as you won’t be closing apps with the back button any more, and you’ll just be sending the app to sleep as you currently see with iOS and Android. To close apps you can now just swipe down on the card from the multi-tasking menu, which is a change that’s long overdue. It’s hard to tell if multi-tasking will be better than what we see from competitors, but what we see improves the experience dramatically. Action Center is also present in the SDK, so expect a significantly better experience with your notifications as well.

Where is Facebook?

When it comes to services, some things are fixed, and some things are oddly missing. Microsoft provides you with the ability to sync with iCloud, which is odd considering Apple’s exclusive mentality, but great if you want to leave iOS for Windows Phone. The odd part is that we can’t see Facebook syncing capabilities anywhere. Windows Phone 7 was famous for including these out of the box, and Windows Phone 8 was notorious for being slow in updating to new Facebook capabilities. In Windows Phone 8.1 there is no sign of it anywhere, even on the photos app. It could be a bug, or this could still be a work in progress, so expect changes here in the future.

YouTube is still not included, but Internet Explorer is updated to version 11 on Windows Phone 8.1, and the new browser fixes the challenges Microsoft has faced with Google. If any Developer has embedded a YouTube video to an app, or if you see this on any service, the app will simply launch the browser and play the video without any issues. If the browser is already open, the video will simply play on the same page as we currently see with Android as well.

Good bye buttons, hello swipes

It’s still not clear if all OEMs will adopt Windows Phone without physical buttons, but the feature is not only available, but also quite smart. As opposed to Android where the buttons are persistently there, Windows Phone gives you an arrow at the left to be able to remove these when you don’t need them. If you need these buttons for any reason, you simply have to swipe from the bottom to reveal them, which is a simple, yet genius update.

Where is Cortana?

One of the biggest reasons why we feel that Facebook might make a comeback, is the fact that we also don’t see Cortana anywhere. We do know of its existence, and we do know that it will launch with Windows Phone 8.1, but it seems that Microsoft has decided to keep it a secret for now. This wouldn’t be the first time the company keeps things until the final launch, for either polish or secrecy, so hopefully a new version of the SDK will reveal it.

Who’s excited?

Microsoft’s changes to Windows Phone 8.1 are not just significant, but also things we’ve asked the company to update for years. This wouldn’t just give the operating system everything it needs to truly compete with iOS and Android, but it would also gives Windows RT an opportunity to be relevant in the tablet space.

While we do expect Nokia to announce at least one Windows Phone 8.1 device at MWC next week, we don’t expect the official launch to happen until the Build 2014 developer conference in April. Are you excited for all of these changes? Please share your thoughts in the comments down bellow, as we’re very excited.